Minibot motors

[baroneje]

Does anyone know how to attach an 3in. long axle directly to the tetrix motor, no gearbox at all?

[Ether]

Originally Posted by baroneje

Does anyone know how to attach an 3in. long axle directly to the tetrix motor, no gearbox at all?

Is it legal to remove the gearbox from the P/N 739023 Tetrix motor, and use the motor (without the gearbox) on the MINIBOT ?

[Colin P]

Originally Posted by Ether

Is it legal to remove the gearbox from the P/N 739023 Tetrix motor, and use the motor (without the gearbox) on the MINIBOT ?

Yes, that's pretty much the only way to get up in less than 3 seconds.


I saw a team put shaft collars onto the remaining gear and then tinker around with that, but it kills the gear.

PVC and (lots of) PVC cement?

[Dad1279]

Originally Posted by Colin P

Yes, that's pretty much the only way to get up in less than 3 seconds.


I saw a team put shaft collars onto the remaining gear and then tinker around with that, but it kills the gear.

PVC and (lots of) PVC cement?

Off the shelf collars would not be legal. We made them by machining a bolt.

[JB987]

Originally Posted by Dad1279

Off the shelf collars would not be legal. We made them by machining a bolt.

R92, S. Indicates "mechanical fasteners" are allowed. A shaft coupler/collar mechanically fastens two shafts together...there were several examples of minibots that passed inspection with such couplers/collars this weekend.

[WileyB-J]

Originally Posted by JB987

R92, S. Indicates "mechanical fasteners" are allowed. A shaft coupler/collar mechanically fastens two shafts together...there were several examples of minibots that passed inspection with such couplers/collars this weekend.

Pretty sure they changed that to "mechanical hardware" in an early update, might wanna check the current version manual.

[EricH]

Originally Posted by WileyB-J

Pretty sure they changed that to "mechanical hardware" in an early update, might wanna check the current version manual.

Nope, they changed it from "mechanical hardware" because all sorts of people were getting confused. It reads "mechanical fasteners".

[joeweber]

We tried this but the motors would smoke.

[Tom Line]

The motors will smoke because your axle is far far too large: you are not gearing correctly for the torque of the motors. It also looks like you're trying to run square shaft through a round bushing, which isn't good at all friction wise.

Round shafts through those bushings with a much smaller OD.

[joeweber]

Originally Posted by Tom Line

The motors will smoke because your axle is far far too large: you are not gearing correctly for the torque of the motors. It also looks like you're trying to run square shaft through a round bushing, which isn't good at all friction wise.

Round shafts through those bushings with a much smaller OD.

It's not a square shaft, It is the shaft that comes with the tetrix kit with a flat spot. If I lathe down the shaft smaller I would still run into the problem of contact with the pole and the friction required to go up it with out slipping. I place rubber electrical tap over this shaft which is legal but there is nothing else small enough that is legal.

[boomergeek]

Originally Posted by joeweber

It's not a square shaft, It is the shaft that comes with the tetrix kit with a flat spot. If I lathe down the shaft smaller I would still run into the problem of contact with the pole and the friction required to go up it with out slipping. I place rubber electrical tap over this shaft which is legal but there is nothing else small enough that is legal.

We found that precision on centering is critical and we had the accuracy of a lathe.

If the shafts are contacting more than about an inch from to the motor, there is significant wobble.
If the load is more than 1.4 lbs per motor, there isn't typically enough of the shaft in contact with the pole to prevent destruction of the tire.

Having the right amount of normal force on the tires is critical. The optimum is a function of the robot weight.

[Captaindan]

if you have extra motors laying around and money to buy more obviously they are going to burn go ahead and take the gearbox off
but a 3sec robot is possible with proper engineering it is totally up to the builder/team

[Al Skierkiewicz]

Joe,
The correct read on R92 is
S. Mechanical fasteners (e.g. screws, bolts, etc),
I would be hard pressed to include COTS shaft couplers in that definition without direct GDC guidance on the subject. Something manufactured from the allowed materials would be OK.

[JB987]

Originally Posted by Al Skierkiewicz

Joe,
The correct read on R92 is
S. Mechanical fasteners (e.g. screws, bolts, etc),
I would be hard pressed to include COTS shaft couplers in that definition without direct GDC guidance on the subject. Something manufactured from the allowed materials would be OK.

Right, Update 3 changed hardware to fasteners...But "etc" is so esoteric, Al! I do agree that someone considering purchase of shaft coupler should check with the GDC though.

[Ether]

Originally Posted by Colin P

Yes, that's pretty much the only way to get up in less than 3 seconds.

Does anybody have a link to the motor curves of the motor without the gearbox?